The present invention relates to a vibration-preventing mechanism and more specifically to a vibration-preventing mechanism for preventing vibration of a resilient contact in a lock type push button switch.
Lock type push button switch devices generally include a plurality of push buttons, resilient contacts having spring quality and disposed so as to correspond to the push buttons and a leaf spring engaging each push button and urging it in the direction opposite the depressing direction. A lock mechanism for holding the push button in the depressed state until another push button is depressed is often provided. In the push button device of this kind, when a given push button is depressed against the spring force of the leaf spring thereby to deform a resilient contact to actuate the switch, the lock mechanism continuously holds the push button in its depressed, i.e. latched, state. When another push button is depressed, any previously latched push button is released, whereupon the push button thus released returns to its non-depressed state and, at the same time, the resilient contact also returns to its initial state to disengage the switch. The depressed push button is in turn latched, thereby actuating the switch corresponding thereto.
In the lock type push button device of the above-described kind, when the push button returns to its non-depressed position, the resilient contact attempts to also return to its initial state due to its own resiliency and follows the return of the push button. Since the contact has a considerable magnitude of resiliency, it often passes its initial state and thereafter tends to return again to the initial, un-stressed state. However, the contact may again pass beyond the initial position due to its resiliency. Thereafter, while repeating this operation, the contact gradually reduces its range of motion and finally comes to rest at the initial position. In other words, the contact may vibrate due to its spring quality. Vibration of the contact results in wear of the contact portion due to chattering, and occurrence of an offensive noise to the operator, or erroneous operation of the switch may result.
Accordingly, it is desired to remove the vibration of the contact in the push button device.